We consider a general Type-I seesaw model with right-handed neutrinos \(N_n\) , the standard model lepton doublets \(l_L\) , and the standard model Higgs doublet \(\widetilde{\phi }=i\tau _2\phi ^\ast \)  as an extension to the Standard Model [1]}, [2]}, [3]}, [4]}, [5]}.
The Lagrangian of the extended section reads,
\(\mathcal {L}_N=\frac{1}{2}\overline{N_n} i\slash {-9.0mu}\partial N_n -\frac{1}{2}\overline{N_n}M_{R\,n}N_n- (y_{\nu j n}\overline{l_{j L}}\widetilde{\phi }N_n + \text{h.c.}),\) 
